IECC Adds Thermal Envelope Language to Code

It’s defined as “the alignment of the air barrier and insulation systems separating conditioned space from unconditioned space.”

Getting it applied to the text of the International Energy Conservation Code (IECC) proved a little more challenging during Tuesday’s ongoing commercial public debate session of the IECC’s annual conference in Atlantic City, but code proponent Robby Schwarz with EnergyLogic was adamant in his determination.

“Representing the building’s thermal envelope on the construction documents ensures that the design professional of the building understands how the thermal envelope will separate conditioned space from unconditioned space,” Schwarz wrote. “This is a crucial step in ensuring not only the energy efficiency of the building, but also the safety, durability, and comfort created in the structure. The simplification of the requirement allows for flexibility in how the building’s thermal envelope is depicted but clearly forces the design professional to understand how what they are drawing will ultimately be constructed.”

The two-part measure, which is not expected to increase construction costs, was eventually passed by both the Commercial Energy Conservation Code Development and Residential Energy Conservation Code Development committees.

The Residential Energy Conservation Code Development Committee, however, initially rejected the measure, calling it “confusing language that would serve to make application of the code more difficult.”

The committee’s decision was easily voted down in the public comment that followed.

Proponents of the new language said the most important energy and performance aspect of the home is the building’s thermal envelope and the alignment of the air barrier and thermal barrier systems. It is crucial, they argued, that the design professional demonstrate an understanding of location of the thermal envelope and that they make an effort to draw its location so that the construction personnel can successfully implement the construction of the building in accordance with the code and the specifications that have been drawn.

There were a few other “big package” residential proposals on Monday, said Dr. Thomas Culp of Birch Point Consulting LLC and the representative for the Glazing Industry Code Committee. RE186 Flex Points proposal from EECC was disapproved by a wide margin. RE188, which creates a new compliance path for homes meeting a certain HERS rating, was approved as submitted.

“It’s a pretty big deal to add a whole new compliance path,” Culp said, “but because it is set at a very high performance level, it may not be used much.”

Also, RE9 was approved with public comment No. 2, which makes an appendix that jurisdictions can optionally adopt to require homes to be “solar-ready.” This doesn’t mean adding solar panels, but, for homes with roof area facing the appropriate direction, setting aside a certain amount of roof as a solar ready zone and ensuring the electrical system can accommodate a future solar energy system.

In other residential news, public comment to RE 20 was withdrawn, meaning it was moved to the consent agenda to be disapproved. RE 19 was also withdrawn, while RE 22 was debated, but failed to garner enough votes for approval.

RE 20 would have mandated higher energy efficiency levels for residential windows in northern zones. The measure was denied by the Residential Energy Conservation Code Development Committee, citing yet-to-be proven technology and the proposed fenestration U-factor as too low.

RE 19 would have reduced the prescriptive U-factor to a maximum of 0.25, while providing five alternatives, U-factor and SHGC combinations that all yield equivalent energy performance to windows having a 0.25 U-factor. Had it passed, RE 22 would have eliminated an alleged code loophole that Culp said actually harms energy efficiency in the North.

“Bottom line,” Culp said, “there were no changes to the U or SHGC requirements for residential windows (not the proposed 0.25 U-factor in the north, nor the proposed minimum SHGC in the north), so they remain the same as in 2012 IECC.”

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